OBJECTIVE: The overall goal of this project is to improve the understanding of the role of dietary carotenoid intake in the etiology and prevention of cancer by applying the USDA-NCI carotenoid database to epidemiologic studies. BACKGROUND: Epidemiologic studies consistently show reduced risk for cancer associated with increased intake of fruits and vegetables, rich sources of carotenoids. To improve dietary assessment of carotenoids in epidemiologic studies, the USDA-NCI carotenoid database was developed and contains values for five carotenoids: alpha-carotene, beta-carotene, cryptoxanthin, lutein/zeaxanthin, and lycopene. Total carotenoid intake can be calculated by summing all five. METHODS: The National Health Interview Surveys have been used to compare dietary carotenoid intake among U.S. adults by demographic and lifestyle characteristics in order to identify high risk groups for chronic disease prevention efforts. The Nurses Health Study has been used to estimate the diet-plasma carotenoid relationship and to estimate the relative risks of breast cancer incidence by level of carotenoid intake alone and in relation to recognized risk factors for breast cancer. PROGRESS: Earlier publications describe the results using The 1987 and 1992 National Health Interview Surveys and an earlier publication from The Nurses Health Study I and the Health Professionals Study describe the relation of diet to plasma carotenoid concentrations in women and men. An earlier publication described the inverse relation of dietary carotenoid intakes and the risk of premenopausal breast cancer among women with a positive family history of breast cancer in a first-degree relative or women at elevated risk due to consuming 15+ g/d of alcohol. Recent analysis identified an inverse relation of dietary carotenoid and vitamin A intakes and risk of premenopausal breast cancer in delayed child-bearers (women who have a first birth at age 30 + years) and in women who have one live birth. Intakes of these nutrients were inversely associated with risk of postmenopausal breast cancer among women who were currently using hormone replacement therapy.